1. Field of the Invention
The invention relates to a method of treating and processing alkaloid-, oil- and protein-containing lupine seeds for the extraction of products from the lupine seeds by means of targeted fractionation, whereby the comminuted lupine seed is de-oiled by introducing a solvent and the residue is depleted of substances soluble in the acid range, preferably of alkaloids, by adding acids.
2. Description of Prior Art
Proteins or protein preparations, respectively, are considered to be raw materials for the food-processing and fodder industries and are used in manifold applications in industrial chemistry, for instance for the production of adhesives, emulsions of photographic layers or cosmetics, just to name some of them.
As proteins are an essential component in animals and plants they are renewable native raw materials suitable for extraction from milk, soybeans and wheat on an industrial scale, for instance. Lupine seeds, which are similar to soybeans in terms of their composition in view of protein level, crude fibre fraction and oil concentration, are particularly important. Lupine cultivation and the processing of lupine seeds for the extraction of desired protein products is therefore of particular interest because lupines can be grown also in regions unsuitable for soy beans, for example in Western Europe or Australia.
Due to plant-inherent bitter principles, the so-called alkaloids, a direct utilization of lupine products is limited, particularly for food applications, and in the case of so-called bitter lupines, which are expedient in terms of cultivation, it is even entirely precluded. When lupine seeds are processed it is therefore necessary to remove the alkaloids in order to obtain products for nutritional use. At the same time, the extracted alkaloids may be selectively employed as active ingredients in agriculture and in the pharmaceutical industry, which renders the complete utilization of lupines or bitter lupines, respectively, extremely interesting from an economic point of view as well.
The German Patent DE 537 265, published in 1931, disclosed, for instance, a method useful utilization of lupines with disembitterment by stepwise extraction with aqueous solutions. Disembitterment is carried out by stepwise extraction of chipped lupines in a moist state, with the addition of an acid and subsequent dissolution of the salts forming in the acid bath.
Moreover, WO 83/00419 discloses a method of and a device for extraction of the bitter ingredients from the seeds of bitter lupines after cold washing of the lupines, which are present in an extremely finely ground condition, with lupine extract solutions of different concentrations, on the counter-flow principle, with water being used as the solvent.
One improved method is disembittering lupine seeds is disclosed in the document WO 97/12524 that provides for an initial thermal treatment of the plant seeds, after comminution of the lupine seeds to grit-like grains having diameters between 200 and 600 μm, so as to achieve a selective deactivation of enzymes present in the plant seeds. The thermal treatment is performed directly by means of a blanching technique, that is by direct introduction of hot steam into the comminuted seeds. After the blanching step, the plant seeds are subjected to a two-stage process for disembitterment, wherein the first extraction step results in the extraction of the alkaloids as well as other anti-nutritive substances. To this end, the plant seeds are mixed with fresh potable water as a solvent in an acid medium in a counter-flow extraction operation. The mixing operation may be preferably carried out in several stages until an extract enriched with anti-nutritive substances and an extractable refined product are obtained, that is rich in proteins and roughage The refined product obtained from the first extraction step is added with water as a solvent in an alkaline medium in a second step. A refined product enriched with roughage as well as a protein milk enriched with proteins are obtained as results of the second extraction step.
All the aforedescribed disembitterment methods are based on a common objective, specifically the objective of extracting, on the one hand, proteins in the purest form possible and, on the other hand, of obtaining roughage for the food or fodder industries, which are disembittered as completely as possible.
The aforedescribed methods, however, present various inherent disadvantages, too: Firstly, plant seeds and lupine seeds in particular have an oil level of roughly 10 to 15%, including lipophilic secondary ingredients such as carotinoids, lecithins or lipophilic alkaloids, in addition to pure oil such as triglycerin.
Even though the known method according to WO 97/12524 proposes a deactivation of the enzymes present in the plant seeds, which precedes the disembitterment process, so that the situation may be precluded that an enzymatic oxidation of exiting unsaturated fatty acids will occur during storage of the disembittered products of this process, which could result in a rancid flavour, for instance, which were inexpedient for application in the food sector, the deactivation is carried out by means of blanching, which means that the plant seeds are exposed to hot steam, which, even though it deactivates the enzymes, on the one hand, creates, on the other hand, unavoidable damage to the storage of proteins as well so that they lose their native form and characteristics.
Finally, the shaping of the comminuted lupine seeds contributes to the success of the disembitterment process, too. The form of grit grains proposed in WO 97/12524 is thus inexpedient insofar as it encloses a comparatively large volume from which the individual components to be extracted must be removed, which means that as the spacing between the interior of the volume and the outside of each grit particle increases, the substances to be extracted are less easily extracted from the grit-shaped lupine seed fragments to be disembittered. On the other hand, WO 83/00419 proposes the grinding of the lupine seeds to be disembittered to produce an extremely fine meal with grain sizes between 1 μm and 50 μm; with this fine grinding of the lupine seeds to form a meal, however, problems occur in terms of process engineering in the separation of the liquid from the solid phase—even though the individual extraction paths inside a “dust grain” are kept very small. This requires complex filtering steps expensive in terms of process engineering, which involve a substantial cost and time factor in application on an industrial scale.
Another known disembitterment process is described in the laid-open German Patent Application DE-OS 29 08 320, wherein the lupine seeds are comminuted and de-oiled. The protein-containing residue produced in that process is subsequently heated and extracted with the addition of an acid. For this known method, too, the aforedescribed disadvantages such as the introduction of water for enzyme deactivation or insufficient comminution of the lupine seeds must be mentioned.
It is also possible to use any protein and oil or starch-containing seed, in addition to the aforementioned lupine seed, such as rape, linseed or leguminous plants, particularly soy-beans, peanuts, peas and horse beans.